1. Technical Field
The present invention relates to a liquid crystal device, an electronic device and a projector.
2. Related Art
The contrast of liquid crystal devices employing a liquid crystal driving method such as a known twisted nematic (TN) mode greatly depends on the viewing angle. In such liquid crystal devices, the contrast of an image viewed straight on is different from that viewed at an angle, and it is impossible to view a good image from an oblique angle. However, such a situation was greatly improved by the development of a lateral-electric-field operation type driving mode called an in-plane switching (IPS) mode or a fringe-field switching (FFS) mode, and a vertical alignment driving mode called a vertical alignment (VA) mode (for example, refer to JP-A-9-80436).
However, even in such liquid crystal devices employing the above-mentioned driving modes to improve the viewing-angle dependent properties, the contrast ratio often drops from 1000:1 or higher when viewed normal to the front display surface to several tens:1 when viewed from an oblique angle. FIG. 19 is a contrast curve showing the viewing-angle characteristics of an IPS mode liquid crystal device. As shown in FIG. 19, a displayed image at a position AR1 near the center of FIG. 19, which corresponds to a displayed image viewed in the normal direction, has high contrast in substantially the entire area thereof. However, a displayed image at a position of AR2 shifted from the center of FIG. 19, which corresponds to a displayed image viewed at an angle of 15 degrees, for example, has low contrast at the corners of the image. Liquid crystal devices employing the FFS mode or VA mode have the same tendency.
Such a decrease in contrast occurring in an image viewed at an angle is disadvantageous in some fields of application, more specifically, in display devices that allows an observer to observe an image from a certain angle off normal to the display surface or that projects an image in a certain direction. Examples of such display devices include, for example, head-up displays (HUDs), head-mounted displays (HMDs), electronic viewfinders (EVFs), and projectors.
An example is shown below. FIG. 20 is a schematic view of a passenger car equipped with an HUD. A head-up display 900 stored in a dashboard 95 of a passenger car includes a liquid crystal device 91 for modulating light emitted from a backlight 92, and a concave mirror 93 for projecting light L (image light) emitted through the liquid crystal device 91 onto a front window 94 to enlarge a displayed image. A front window shield 96 that reflects the projected light L toward an occupant M is disposed on the front window 94. The occupant M observes a virtual image I formed by the light L reflected by the front window shield 96.
At this time, outside light SL, such as sunlight, entering the liquid crystal device 91 through the front window 94 is specularly reflected (mirror-reflected) by the liquid crystal device 91 at the surface adjacent to the concave mirror 93 toward the occupant M along the same optical path as the light L emitted from the backlight 92, and makes it difficult to view an image on the HUD.
To counter this situation, a structure is proposed in which the liquid crystal device 91 is disposed obliquely to allow the outside light SL reflected by the liquid crystal device 91 at the surface adjacent to the concave mirror 93 to be guided in the direction which the occupant M cannot see. However, in such a structure, the contrast of the displayed image decreases greatly because of the viewing-angle dependent properties, and it is impossible to display images properly.
Although a proposal for improving reflection of the outgoing light in the device using the structure of the liquid crystal device has been made by, for example, JP-A-5-53090, a proposal for correcting the problem in the relationship between the outside light and the displayed image using the structure of the device has not been made. Therefore, there are demands for liquid crystal devices having good display characteristics when viewed from a certain viewing-angle, not in a direction normal to the liquid crystal device, developed on the basis of a design concept that is different from that of a known liquid crystal device.